1. Field of the Invention
This invention relates to circuit breakers, and more particularly, to a breaker in which the rated current level is preset by a removable cam element.
2. Description of the Prior Art
Circuit breakers which provide over-current protection are well known. Small capacity breakers for household electrical service have substantially replaced the use of fuses. Generally such circuit breakers are built to provide a predetermined rated capacity. Breakers for individual circuits may have a rated capacity of 10 or 15 amperes. In addition, the service may have a main breaker with a predetermined capacity of, for example, 100, 150 or 200 amps., etc. The main breaker generally includes two trip units connected respectively in series with the two ungrounded lines of the standard three-conductor 220 volt service. The main breaker is a relatively expensive unit. Providing a number of different breakers to provide a range of rated capacities adds to the production and inventory cost. Therefore, it is desirable to provide a main breaker in which the rated capacity may be set at the time the breaker unit is sold to the installer or whose capacity can be changed even after installation.
While variable capacity breakers have been proposed, such known breaker units have utilized current monitoring transformers and solid-state sensors for actuating the trip mechanism when the current through the monitoring transformers reaches a predetermined level. Circuit breakers of this type are more complex and costly and so for this reason are not normally utilized in household type service.